1. Field of the Invention
This invention relates to a reverse rotation preventing device, and more particularly to a technique of preventing the reverse rotation transmitted from the driven side to the driving side, effectively utilized, for example, in a power window mechanism for opening or closing a window in a vehicle by means of a motor.
2. Related Art Statement
As a reverse rotation preventing device for preventing opening a window from the side of a window glass in a power window mechanism, there are known ones described in Japanese Patent Application Laid-Open No. 60-245841 and U.S. Pat. No. 3757472.
With these reverse rotation preventing devices, when the driving force from a motor acts on a rotating body on the input side, an engageable portion provided on the rotating body is engaged with an engageable pawl of a coil spring to decrease the diameter of the coil spring, whereby the coil spring is released from contact with a ring member, so that the driving force from the motor is transmitted to a rotating body on the output side through the rotating body on the input side, thereby driving a window opening-closing mechanism.
On the contrary, when an improper force from the window opening-closing mechanism acts on the rotating body on the output side, an engageable portion of the rotating body is engaged with an engaging pawl of the coil spring to increase the diameter of the coil spring, whereby the coil spring is pressed against the ring member, so that a rotary shaft of the motor is prevented from rotating due to the improper force from the power window mechanism.
Further, in these reverse rotation preventing devices, the coil spring is covered with reinforcing rings on opposite sides of the coil spring in the axial direction to prevent the engaging pawl of the coil spring from being deformed when a considerable force acts on the engaging pawl.
However, in these conventional reverse rotation preventing devices as described above, the engaging pawl of the coil spring is bent to project in the diametral direction toward the center of the coil spring, whereby, when the bending accuracy of the engaging pawl of the coil spring is low, sometimes, there may be cases where the diameter decreasing action and diameter enlarging action of the coil spring becomes improper.